Many applications require plaintext information, for example data and/or program code, to remain within a single chip/device in order to reduce the risk of unauthorized disclosure of confidential or secret information. Information may be authenticated and stored off-chip in ciphertext form to prevent snooping and/or injecting malicious information. In some systems, specialized CPUs are employed to authenticate and decrypt information received from an off-chip memory device. The specialized CPUs may be slower than desired, because the same processor that executes instructions may also have to perform decryption tasks. Time spent decrypting is time not spent performing core tasks of the application.
Though advances in circuit integration are providing increasing quantities of on-chip memory, in many instances, the amount of on-chip memory is insufficient to fully store application information. Programmable integrated circuits (ICs) are examples of systems on a chip (SOCs) that have on-chip memory for application use. Generally, programmable ICs are devices that can be programmed to perform specified logic functions. A programmable IC may include programmable logic or a combination of programmable logic and hardwired logic, such as one or more microprocessors. One type of programmable IC, the field programmable gate array (FPGA), typically includes an array of programmable tiles. These programmable tiles comprise various types of logic blocks, which can include, for example, input/output blocks (IOBs), configurable logic blocks (CLBs), dedicated random access memory blocks (BRAM), multipliers, digital signal processing blocks (DSPs), processors, clock managers, delay lock loops (DLLs), bus or network interfaces such as Peripheral Component Interconnect Express (PCIe) and Ethernet and so forth.
Each programmable tile may include both programmable interconnect and programmable logic. The programmable interconnect typically includes a large number of interconnect lines of varying lengths interconnected by programmable interconnect points (PIPs). The programmable logic implements the logic of a user design using programmable elements that can include, for example, function generators, registers, arithmetic logic, and so forth.
The programmable interconnect and programmable logic are typically programmed by loading a configuration data stream into internal configuration memory cells that define how the programmable elements are configured. The configuration data can be read from memory (e.g., from an external PROM) or written into the FPGA by an external device. The collective states of the individual memory cells then determine the function of the FPGA.
Some programmable ICs include one or more microprocessors that are capable of executing program code. The microprocessor can be fabricated as part of the same die that includes the programmable logic circuitry and the programmable interconnect circuitry, also referred to collectively as the “programmable circuitry” of the IC. It should be appreciated that execution of program code within a microprocessor is distinguishable from “programming” or “configuring” the programmable circuitry that may be available on an IC. The act of programming or configuring programmable circuitry of an IC results in the implementation of different physical circuitry as specified by the configuration data within the programmable circuitry. An SOC is an example of a programmable IC and may include a micro-processor, programmable logic, on-chip memory, various input/output (I/O) circuitry, and interconnect circuits for communicating between the micro-processor, programmable logic, and I/O circuitry.